In-Depth NMR Investigation of the Magnetic Hardening in Co Thin Films Induced by the Interface with Molecular Layers

The hybridization of the surface orbitals of thin ferromagnetic layers with mole-cular orbitals represents a soft but efficient technology that is able to induce in ferromagnetic component radical modifications of the key magnetic param-eters, such as magnetization, magnetic anisotropy, and others. These effects are investigated in 7 nm thick polycrystalline Co films interfaced with C60 and Gaq3 molecular layers by combining 59Co Ferromagnetic nuclear resonance spectroscopy (FNR) and magneto-optic kerr effect (MOKE) techniques. It is demonstrated that the surface hybridization produces a significant magnetic hardening with respect to a reference Co/Al system and that the molecule-induced effects modify the magnetic properties of entire Co layer, propagating for several nm from the interface. The FNR spectroscopy also reveals a recon-struction of the magnetic environment at the cobalt surface, whose observa-tion in polycrystalline films is especially intriguing. The results shed new and unexpected light on the interfacial physics in such systems, whose under-standing necessitates further experimental and theoretical research.